This invention relates to a window unit with decorative bars of the type known as muntin bars.
In recent years windows have become generally larger and particularly in colder climates have been manufactured as sealed window units including two or more panes which are spaced by spacer strips. Examples of this type of structure are described in co-pending U.S. application Ser. Nos. 512,469 and 630,275, (now U.S. Pat. Nos. 4,564,540 and 4,551,364) the disclosures of which are incorporated herein by a reference.
For decorative reasons it has also become popular in recent years to divide the large expanse of window into separate portions to simulate the small panes which were essential in previous years due to inadequate construction techniques that have since been considered attractive in certain styles of houses.
The large expanse of window pane is thus in many cases divided up into small square or rectangular cells by a frame or strip structure in many cases manufactured from wood and inserted inwardly of the inner sheet of glass so as to sit within the window frame. However, such a construction is often a dust trap and even though they can in many cases be removed they are difficult to clean and difficult to keep in good order.
Other arrangements have also been proposed and sold in which a frame structure is manufactured during the construction of the sealed window unit and is positioned inside the sealed window between two panes of glass. Of course such a construction keeps the frame out of the moving atmosphere and this avoids any collection of dust. Various materials have been proposed for such a construction including metal for example aluminum or steel and wood. Vinyl and other plastics have not been suitable since they generally have a very high coefficient of expansion and thus when heated by sunshine on the window can warp and otherwise distort. In addition, plastics of this type tend to give off monomer gases which can condense on a window pane and cause staining or coloring of the glass.
The steel and aluminum structures which have been proposed are expensive to construct since they must be manufactured by corner pieces or by other integral joints. In addition they provide thermal bridging between the glass panes and have unsatisfactory coefficients of thermal expansion which can cause problems.